Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F9/00—Compounds containing elements of Groups 5 or 15 of the Periodic Table
  • C07F9/02—Phosphorus compounds
  • C07F9/28—Phosphorus compounds with one or more P—C bonds
  • C07F9/38—Phosphonic acids [RP(=O)(OH)2]; Thiophosphonic acids ; [RP(=X1)(X2H)2(X1, X2 are each independently O, S or Se)]
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F9/00—Compounds containing elements of Groups 5 or 15 of the Periodic Table
  • C07F9/02—Phosphorus compounds
  • C07F9/28—Phosphorus compounds with one or more P—C bonds
  • C07F9/38—Phosphonic acids [RP(=O)(OH)2]; Thiophosphonic acids ; [RP(=X1)(X2H)2(X1, X2 are each independently O, S or Se)]
  • C07F9/3804—Phosphonic acids [RP(=O)(OH)2]; Thiophosphonic acids ; [RP(=X1)(X2H)2(X1, X2 are each independently O, S or Se)] not used, see subgroups
  • C07F9/3808—Acyclic saturated acids which can have further substituents on alkyl

Definitions

• This invention relates to a chemical process and in particular a process for the manufacture of N-phosphonomethyliminodiacetic acid.
• N-phosphonomethyliminodiacetic acid is a known compound useful in the manufacture of N-phosphonomethylglycine and certain salts thereof which are active as herbicides.
• Example IV describes a process in which the hydrochloride of aminodiacetic acid (a compound referred to herein as iminodiacetic acid) in the presence of concentrated hydrochloric acid and orthophosphoric acid is heated to 100°C and then reacted with 38% aqueous formaldehyde solution followed by paraformaldehyde.
• the product is described as N,N-diacetic acid aminomethylenephosphonic acid but is referred to herein as N-phosphonomethyliminodiacetic acid.
• N-phosphonomethyliminodiacetic acid Many other processes for the manufacture of N-phosphonomethyliminodiacetic acid are known, including for example that described in United Kingdom Patent No 2 154 589 in which an alkali metal salt of iminodiacetic acid such as the sodium salt is reacted with a strong mineral acid such as sulphuric acid to form the strong mineral acid salt of iminodiacetic acid and the alkali metal salt of the acid (for example sodium sulphate).
• the strong mineral acid salt of iminodiacetic acid is then reacted with formaldehyde and phosphorous acid and sufficient water to dissolve the alkali metal salt whilst the N-phosphonomethyliminodiacetic acid product is precipitated.
• the filtrates from the reaction of iminodiacetic acid with phosphorous acid and formaldehyde may be re-cycled a plurality of times without excessive build-up of by-product, provided that sulphuric acid is used as mineral acid and provided that the starting material is iminodiacetic acid and not an alkali metal salt thereof.
• N-phosphonomethyliminodiacetic acid which comprises :
• stages (1) to (5) above may represent hypothetical stages in a continuous reaction wherein filtrate stream is continuously re-cycled to the reaction vessel (optionally via a water removal stage) and wherein reactants are continuously charged to the reaction vessel and N-phosphonomethyliminodiacetic acid product which precipitates is removed by continuous or semi-continuous filtration.
• the use of the re-cycle reaction of the present invention will generally have the effect of reducing the waste/effluent stream produced in the process and of making most effective use of the starting materials.
• the source of formaldehyde is suitably either an aqueous solution of formaldehyde or paraformaldehyde, depending on the proportion of water which is desired to be added. If water is removed from the filtrates in stage (3), it may be desirable to use paraformaldehyde in subsequent reaction stages (1), thereby reducing the proportion of water which it is necessary to remove.
• the phosphorous acid may be introduced into the reaction as a solid (for example as a flaked solid), as a molten liquid or as an aqueous solution, for example as a commercially available aqueous solution typically containing 70% by weight of phosphorous acid.
• water is removed in stage (3) and suitable methods for the removal of water include for example distillation of the filtrates from stage (2) or the use of semi-permeable media.
• the distillation of the filtrates may take place at atmospheric pressure at the boiling point of the filtrate medium, typically of the order of 140°c by the time the distillation is completed. We have found that distillation at atmospheric pressure is satisfactory and permits multiple re-cycles. It may however, be desirable to reduce the possible formation of by-products by operating the distillation stage under reduced pressure and at a correspondingly lower boiling point of the filtrate medium. The possibility of a reduced formation of by-products must be offset against the added cost of operation at reduced pressure.
• the distillation of the filtrate medium takes place at a temperature of from 20°C-140°C, for example 60°C-140°C, and especially from 60°C-90°C or more particularly from 40°C to 100°C, the pressure being reduced accordingly.
• the solid N-phosphonomethyliminodiacetic acid product which is recovered by filtration from stage (1) may be washed to remove filtrate medium adhering thereto. If desired at least a proportion of such washings may be added to the filtrates and the term "filtrates" and "filtrate medium” as used herein is to be understood to include such washings if present. It is to be noted however, that the addition of washing to the filtrates will increase the proportion of water which is to be optionally removed in stage (3) and that the addition of the washings to the filtrate stream may not always therefore be desirable.
• any formaldehyde present in the filtrates may be removed during the distillation stage (if present). If desired, formaldehyde may be recovered during the distillation stage and may be returned to the reaction stage (1). However, the re-cycle of formaldehyde is not necessary and does not form an essential part of the present invention.
• reaction conditions used during the reaction stage (1) are essentially conventional. Substantially stoichiometric proportion of reactants may be used although it may be desirable to use a slight molar excess relative to iminodiacetic acid. Thus it is preferred to use from 1-1.5 moles of phosphorious acid per mole of iminodiacetic acid, for example 1.1 mole of phosphorous acid per mole of iminodiacetic acid. Similarly, it is preferred to use from 1-2 moles of formaldehyde per mole of iminodiacetic acid, for example 1.2 mole of formaldehyde per mole of iminodiacetic acid.
• Sulphuric acid is not consumed as a primary reactant during the reaction and sufficient sulphuric acid should be used to provide an appropriate reaction rate.
• Sufficient water should be used to ensure a mobile reaction medium. In general up to 10 or more moles of water per mole of iminodiacetic acid may be used, but the proportion of water necessary to provide an effective reaction medium may be readily determined by those skilled in the art.
• the source of formaldehyde to a pre-mixture of the iminodiacetic acid, phosphorous acid and sulphuric acid. If aqueous formaldehyde is used as the source of formaldehyde, water will be added with the formaldehyde.
• a typical commercially available aqueous formaldehyde solution contains for example from about 36%w/w to 50% w/w formaldehyde together with for example about 0.5-15%w/w methanol as stabiliser.
• the reaction temperature is typically from 50°C to 150°C, for example from 105°C to 125°c or more particularly from 110°C to 120°C.
• Lower reaction temperatures for example reaction temperatures below 100°C, may have the advantage of reducing the level of any by-products formed during the reaction but this will tend to be offset by a reduced rate of reaction. It then may be advantageous to adjust the process conditions in favour of an increased reaction rate, for example by increasing the proportion of sulphuric acid in the reaction mixture.
• a purge of for example from up to 25% to 40% or more of the filtrates stream may be used but in general it is preferred not to use a purge stream greater than 50% and a purge stream of up to 40Z of the filtrates stream may be typical, although of course it may be possible to reduce the level of any by-products (as described herein) such that even lower purge levels may be used or even no purge at all.
• a corresponding purge stream may be used in continuous operation.
• reaction mixture was allowed to cool to 25 °C over 90 minutes and the reaction mixture was filtered.
• the filter cake was washed with water (57ml) and the product was dried in a vacuum oven to yield 67.9g of N-phosphonomethyliminodiacetic acid at 98.0% strength, equivalent to an isolated yield of 59.82.
• the filtrates (128.0g) and the water wash (66.0g) were analysed at 13.7% and 5.5% N-phosphonomethyliminodiacetic acid respectively. This was equivalent to a total conversion yield of 78.9% N-phosphonomethyliminodiacetic acid.
• the filtrates (122.3g) from Cycle 1 were recharged to the reaction flask and the apparatus was adapted for distillation.
• the filtrates were heated to boiling point and 27g of distillate was removed taking the final temperature of the pot contents to 140 °C.
• the concentrated filtrates were then used in Cycle 2.
• reaction mixture was allowed to cool to 25 °C over 90 minutes.
• the reaction mixture was filtered and the filter cake washed with water (57ml).
• the product was dried in a vacuum oven to yield 102.2g of N-phosphonomethyliminodiacetic acid at 95.4% strength equivalent to a cumulative isolated yield of 75.3%.
• the filtrates (99.3g) and the water wash (76.8g) were analysed at 7.5% and 3.7% N-phosphonomethyliminodiacetic acid respectively. This was equivalent to a total cumulative conversion yield of 81.7% N-phosphonomethyliminodiacetic acid.
• the filtrates (95.1g) from reaction 1 were recharged to the reaction flask and the apparatus was adapted for distillation.
• the filtrates were heated to boiling point and 20.5g of distillate was removed taking the final pot temperature to 140 °C.
• the concentrated filtrates were then used in Cycle 3.
• the reaction mixture was filtered and the filter cake washed with water (57ml).
• the product was dried in a vacuum oven to yield 90.lg of N-phosphonomethyliminodiacetic acid at 95.6% strength equivalent to a cumulative isolated yield of 78.2%.
• the filtrates (91.lg) and the water wash (71.8g) were analysed at 5.0% and 3.0% N-phosphonomethylimiodiacetic acid respectively. This was equivalent to a total cumulative conversion yield of 82.3% N-phosphonomethyliminodiacetic acid.
• the reaction mixture was then heated to 120 °C and formaldehyde (42.8g at 36.1% strength, 0.515 moles) was then added over one hour. The temperature was maintained between 110 and 120 °C during addition. On complete addition the reaction mixture was allowed to cool to 25 °C over 90 minutes. The reaction mixture was filtered and the filter cake washed with water (57ml). The product was dried in a vacuum oven to yield 66.2g of N-phosphonomethyliminodiacetic acid at 91.4% strength equivalent to a cumulative isolated yield of 74.2%. The filtrates (92.8g) and the water wash (70.7g) were analysed at 5.4% and 4.2% N-phosphonomethyliminodiacetic acid respectively. This was equivalent to total cumulative conversion yield of 78.2% N-phosphonomethyliminodiacetic acid.
• Example 1 a proportion of the filtrates in each cycle was removed for anlysis. Subsequent reactions were scaled down accordingly.
• reaction mixture was heated to 115 °C and formaldehyde (48.2g at 37.0% strength, 0.594 moles) was added over two hours. The temperature was maintained between 110 and 120°C during addition. On complete addition, the reaction mixture was held at 115°C for a furthre hour and then allowed to cool to 90°C. A second water charge (92.0 g) was added over 1 hour maintaining the temperature at approximately 90°C during the addition. The reaction mixture was allowed to self-cool overnight.
• formaldehyde 48.2g at 37.0% strength, 0.594 moles
• the combined filtrates and wash liquors (236.0 g) were charged to a stirred 500 ml flask set up for vacuum distillation.
• the equipment was evacuated to a pressure of 50 mm Hg and gradually warmed to distill off water until the flask temperature rose to 100°C.
• the residue (71.6 g) was cooled and analysed for N-phosphonomethyliminodiacetic acid (9.1%) and moisture content (14.9%).
• cycle 1 The procedure of cycle 1 was then followed to yield 107.6g of dry product at 98.9% strength, equivalent to an isolated yield of 97.9%.
• the filtrate (179.6g) and wash (54.8g) contained 2.61% and 1.66% N-phosphonomethyliminodiacetic acid respectively; the total yield, minus the N-phosphonomethyliminodiacetic acid recycled with the filtrate, gave a stage conversion yield of 97.4%.
• Cycle 2 The procedure as for Cycle 2 was repeated for Cycles 3 to 8, adjustments being made for the water content of the concentrated filtrate (equivalent to 90% recycle in each case), as follows.
• PIDA is used for N-phosphonomethyliminiodiacetic acid.
• the combined filtrates and wash liquors (229.0 g) were charged to a stirred 500 ml flask set up for vacuum distillation.
• the equipment wa evacuated to a pressure of 50 mm Hg and gradually warmed to distill off water until the flask temperature rose to 100°C.
• the residue (72.6 g) was cooled and analysed for N-phosphonomethyliminodiacetic acid (7.1%) and moisture content (17.6%).
• Cycle No. Scale (Moles IDAA) Concentrated Filtrate+Wash Water Added g Isolated Product Conversion Weight used g Water content % PIDA content % Strength % Yield % Yield % 3 0.423 68.6 14.5 6.6 Nil 92.8 89.9 90.3 4 0.388 67.6 13.7 8.0 Nil 94.1 91.0 89.7 5 0.352 71.4 19.9 6.9 Nil 93.8 88.6 87.5 6 0.324 66.5 10.7 6.2 0.5 91.8 84.0 83.0 7 0.293 68.5 11.5 6.7 Nil 95.6 82.3 80.9 8 0.260 69.7 7.1 5.3 Nil 89.2 62.0 55.8 Note: The fact that conversion yields appear, after the third cycle, always to be lower than isolated yields, is probably due to the difficulty of estimating N-phosphonomethyliminodiacetic acid in relatively impure filtrate samples.
• the combined filtrates and wash liquors (224.2 g) were charged to a stirred 500 ml flask set up for vacuum distillation.
• the equipment wa evacuated to a pressure of 4-25 mm Hg and gradually warmed to distill off water until the flask temperature rose to 100°C.
• the residue (70.2 g) was cooled and analysed for N-phosphonomethyliminodiacetic acid (11.3%) and moisture content (15.3%).
• the combined filtrates and wash liquors (227.8 g) were charged to a stirred 500 ml flask set up for vacuum distillation.
• the equipment wa evacuated to a pressure of 50 mm Hg and gradually warmed to distill off water until the flask temperature rose to 100°C.
• the residue (68.8 g) was cooled and analysed for N-phosphonomethyliminodiacetic acid (6.5%) and moisture content (14.2%).
• the combined filtrates and wash liquors (222.2 g) were charged to a stirred 500 ml flask set up for vacuum distillation.
• the equipment wa evacuated to a pressure of 40 mm Hg and gradually warmed to distill off water until the flask temperature rose to 100°C.
• the residue (71.1 g) was cooled and analysed for N-phosphonomethyliminodiacetic acid (10.3%) and moisture content (17.1%).
• the combined filtrates and wash liquors (243.0 g) were charged to a stirred 500 ml flask set up for vacuum distillation.
• the equipment wa evacuated to a pressure of 50 mm Hg and gradually warmed to distill off water until the flask temperature rose to 100°C.
• the residue (87.3 g) was cooled and analysed for N-phosphonomethyliminodiacetic acid (7.0%) and moisture content (16.8%).
• the filtrate (142.6g) and wash (66.0 g) contained 1.3% and 1.2% N-phosphonomethyliminodiacetic acid respectively; the total yield, minus the N-phosphonomethyliminodiacetic acid recycled with the filtrate, gave a stage conversion yield of 95.8%.

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• 1993
  • 1993-01-14 GB GB939300641A patent/GB9300641D0/en active Pending
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• 1994
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